The invention concerns a machine tool, for example a lathe.
Machine tools such as lathes usually have a bed on which are arranged individual modules of the machine, for example one or more tool carrier systems, one or more workpiece carrier systems, measuring units, loading and unloading devices and so forth.
For that reason the bed must be designed to be as inherently strong and stable as possible as it is only in that way that it is possible to achieve high levels of machining accuracy on the workpieces produced on the machine tool.
In order to be able to displace the modules of the machine in the longitudinal direction of the bed, which is referred to generally and therefore also herein as the Z-direction, arranged on the bed are guide tracks on Which those modules of the machine run.
In this respect, different forms of bed are known, for example in the case of lathes the beds may be cradle beds, inclined beds, vertical beds and overhanging beds and so forth. The beds however generally stand flat on a base plate or on the foundation ground on which the machine tool is supported.
In that respect the different forms of bed serve on the one hand to achieve a good discharge flow of the cuttings and chips which are produced in the machining operation, while on the other hand serving to achieve the highest possible level of stability, in particular from dynamic points of view, for the bed.
A problem in that respect is also the supply of energy to the machine modules which are guided on the top side or at the front side of beds of that kind, the modules in turn having motors, for example for driven tools, for movement of the tool carrier unit, for example a tool turret, and so forth.
What is critical in that respect is in particular the energy supply to the machine modules which are disposed at a low level and which are below the machining position, as the energy feed means for same, which have to be flexible in design because of the longitudinal displaceability involved, are in the region into which the chips and turnings fall.
An object of the invention is to provide a machine tool which, in spite of the possibility of simple and inexpensive manufacture thereof, permits a highly variable layout and fitment of the machine tool with machine modules and which moreover in spite of a good discharge of chips and turnings permits a simple supply of energy with a low level of susceptibility to trouble, in particular to the lower machine modules.
A further object of the invention is to provide an improved machine tool which affords structural strength in particular in respect of its bed and which is of a rational design configuration adapted to afford versatility in terms of fitting equipment items thereto.
Still another object of the invention is to provide a machine tool having a bed of enhanced rigidity while not impeding the fitment of and movement of operating units thereon and the movement of supply lines and conduits for same.
Those objects are attained by the invention set forth herein. Advantageous embodiments are set forth in the appendant claims.
By virtue of the bed being stood up to form a portal bed, in particular on only two feet at the ends of the bed, all kinds of energy feed means can be passed in virtually any amount transversely beneath the bed and displaced in the longitudinal direction together with the machine modules which they supply. That avoids limitations as to whether and which machine modules are used on the lower part of the bed, therefore in particular beneath the machining position.
Hitherto standing the bed up to form a portal bed in that way was faced with the prejudice that a machine tool achieves correspondingly better machining results, the more stable that the bed and the substructure carrying the bed is, in particular in relation to vibration and oscillations. For that reason hitherto beds were generally supported over the full surface area or on a large number of contact points, in relation to the foundation ground.
By virtue of the fact that the support feet of the machine tool of the invention are only of very small height, just sufficient for the energy supply lines such as electrical cables, hydraulic conduits, pneumatic hoses etc to be passed through beneath the bed, it is possible on the one hand to achieve a bed cross-section which is of a great height and which thus enjoys a high level of stiffness in relation to flexing without on the other hand the machining position, for example the turning center of a lathe, being disposed at an excessively great height for the operator who stands in front of the machine, even if the machining position is in the upper heightwise region of the bed, in particular in the upper half thereof, because a lower tool support is provided in the lower region.
Because the portal bed is of an approximately rectangular cross-section, or at any event has outsides, in particular for example the top side and the front side, which are at a right angle relative to each other and which carry the individual guide tracks, machining of the bed can be implemented easily and inexpensively. By virtue of guide tracks which extend thereon exclusively in the Z-direction and by virtue of using identical guide tracks, it is possible on the one hand to achieve a further reduction in cost, while on the other hand the individual machine modules can be fitted on different guide tracks. For that reason all guide tracks in both transverse directions (X-direction and Y-direction) with respect to the direction of displacement of the machine modules, being therefore the Z-direction, are of a positively locking configuration, in particular of such a configuration as to engage behind their components sliding thereon.
In addition the portal bed has through openings which are continuous in the longitudinal direction and which are open on both sides and which can also serve for the passage therethrough of lines and conduits, for example energy supply conduits, from one end of the machine to the other. When the structure is made of plastic material or a concrete-plastic mix, the through openings generally comprise two or three mutually superposed circular through openings, while when the portal bed is made from cast steel the through openings remain between the surrounding, peripherally extending outer shell and the ribs formed in one piece therewith, generally therefore being two or three large hollow chambers. The cross-section of the portal bed is preferably between 1.5 and 3 times as high and in particular between 1.8 and 2.2 times as high as the depth of the portal bed and guides are preferably arranged only on the top side and the front side, more specifically with a pair of guides on the top side and two pairs of guides at the front side.
In a preferred embodiment the pairs of guides at the front side are at different guide track spacings, but the pairs are relatively close together one above the other.
In another preferred embodiment of this structure the spacing of the guide tracks within the pairs is identical and the spacing of the pairs relative to each other likewise, so that overall only identically spaced guides and preferably four guide tracks are arranged at the front side.
Preferably, no guide tracks are arranged at the underside, in order not to increase the necessary height of the feet of the bed.
At best a guide track could also be arranged at the front edge of the underside, whereby however a machine module would only slightly engage around the lower front edge of the bed. Machine modules guided completely along the underside, that is to say by means of guide tracks arranged at the front and rear edges of the underside, would result in an increase in the support height and would involve the disadvantages that this entails. Provided between the individual guide tracks, also extending in the longitudinal direction and in particular being continuous, are channel-shaped recesses in the surface of the portal bed, which serve to receive the ball rolling spindles for driving the machine modules in the longitudinal direction or other transmitting drive elements.
In order to protect the guide tracks from contamination, preferably telescopic covers are arranged in the longitudinal direction, which preferably always jointly cover a pair of guide tracks, that is to say for example the pair of guide tracks which is arranged on the top side.
In order to prevent chips and turnings from being squeezed in between two mutually adjoining mutually telescopic covers, intermediate covers are arranged between the individual covers which are arranged in superposed relationship in respect of height and which are each telescopic in themselves in the longitudinal direction. The intermediate covers are in particular fixedly mounted and are non-telescopic, while the telescopic guide cover which is disposed thereover and the guide cover which is arranged therebeneath engage the intermediate cover from two different sides. In this case the intermediate cover extends in an inclinedly downward position or even vertically in order to prevent the ingress of chips and turnings between the individual covers.
The bed feet are preferably not a component part of the bed but separate individual parts. The portal bed preferably stands on a base plate which is in the form of a welded structure and the bed feet are preferably also welded structures which are screwed on the base plate or which are formed in one piece together therewith. In that respect relative displacement of the bed with respect to the assembly carrying it, that is to say for example the base plate, by virtue of thermally induced expansion of the bed in the machining operation, must be possible, for example by virtue of suitable clearance in the screws.
Additional devices such as the required switch cabinets and energy supply devices such as hydraulic and pneumatic pumps and the like are preferably also disposed on such a base plate, behind the bed of the machine tool, and a loading and unloading system for the machine is also fixed either on the base plate or directly at the end to the machine bed. In that case the switch cabinets and energy supply devices can be positioned as closely as possible to the rear of the bed or can be at such a large spacing in relation thereto that a service passage or corridor is afforded therebetween, from which service personnel at the rear of the machine can carry out maintenance and repair operations or observe the machine while it is operating.
In that respect the additional devices, that is to say switch cabinets and energy supply devices, can preferably be mounted on the bed or the base plate by means of an auxiliary structure, which can be referred to as the switch cabinet frame structure, more specifically optionally in the position which is as close to the machine as possible or the position which is spaced therefrom in order to afford the service passage or corridor, depending on the respective ground floor area available at the user of the machine.
In all cases in that respect the machine is transported in the fully assembled condition, that is to say in the form which can be referred to as xe2x80x98hook machinexe2x80x99, in that the entire machine assembly can be lifted in its entirety by a crane hook, preferably however with the additional units in the position of being moved close to the bed, insofar as the bed with all machine modules and ancillary units thereon is lifted for example by a crane hook and the additional units are moved into the position of being spaced from the bed only after the machine has been set up at its position of use.
Furthermore, even when the switch cabinets which are generally arranged over the entire longitudinal extent of the machine are arranged close to the bed, there must still be sufficient space between the cabinets and the rear of the bed for energy supply lines and conduits there, for example trailing cable arrangements. Trailing cable arrangements which supply energy to the lower and upper tool modules respectively are arranged in particular at the height of the upper edge and the lower edge respectively of the portal bed.
Those trailing cable arrangements can without any problem supply energy in particular to a tool unit which is longitudinally guided on the top side of the portal bed and a tool unit which is guided on the lower pair of guides at the front side.
The chips and turnings produced are removed by means of a chip conveyor which is arranged at a suitable depth directly in front of the front side of the machine bed. For that purpose, when using a base plate, it has a bevelled upper front edge and the portal bed is mounted so far forwardly on the base plate that its front edge is already disposed above that bevel configuration of the base plate.
A workpiece unit in particular a headstock or a tailstock longitudinally guided on the upper pair of guides at the front side is therefore preferably so designed that it manages without any supply of energy, for example insofar as the longitudinal movement is produced by means of a mechanical component, for example a ball roll spindle, and the workpiece is held passively, for example in the case of a tailstock, by means of a spring biasing force in respect of the tailstock sleeve in relation to the tailstock housing. In that way, in the case of a machine module which is movable in the longitudinal direction, it is possible to avoid an energy supply means movable therewith, at the center of the height of the machine tool. A portal bed which is highly uniform in regard to its stability by virtue of its rectangular shape, with identical Z-guides extending in parallel relationship, can be used for different machine structures.
A preferred embodiment is in the form of a lathe in which in particular the headstock and possibly the additional tailstock is guided at the front side of the portal bed in the upper region while machine modules, generally tool slide systems, are guided in the lower region and on the top side. In that case, as viewed from the front side of the machine, there may even be two such units on each of the same guide tracks, that is to say to the right and to the left of the workpiece.
While in the case of the conventional design configuration in that case the spindle axis is directed in the Z-direction, it is also possible to adopt a transverse arrangement, that is to say for example in a vertical direction referred to as the X-direction, in particular if the headstock in that case is guided along the guide tracks at the top side of the portal bed.
An embodiment in the form of a milling machine with a tool mounting arrangement in the upper region of the front side of the portal bed is also possible, with milling units which are guided along the guide tracks at the top side. If in addition the unit carrying the workpiece is longitudinally guided in the lower region of the portal bed, the longitudinal guides of the upper region at the front side are additionally available for tool modules, measuring modules or the like. That also makes it possible for the machine to be in the form of a hybrid milling/turning machine, that is to say, both with tool modules which are pure milling modules and also with tool modules which correspond to those of a lathe, that is to say which carry a tool turret with turning blades and possibly additional driven tools.